UV-C irradiation enhances the dual-use potential of Desmodesmus quadricauda and Scenedesmus dimorphus for food and biodiesel production

UV-C irradiation was evaluated as a strategy to enhance the dual-use potential of green microalgae Desmodesmus quadricauda and Scenedesmus dimorphus for functional food and biodiesel applications. Cultures were exposed to UV-C for 0–3 h and cultivated for 14 days. Biomass production increased significantly, reaching maxima at 3 h in D. quadricauda (1.63 ± 0.10 g L −1 ) and at 1 h in S. dimorphus (1.27 ± 0.05 g L −1 ). UV-C irradiation markedly enhanced carotenoid content and increased protein levels by 1.2–1.3-fold, suggesting improved nutritional value. Lipid content and productivity peaked at 1 h in both species, with 1.4–1.9-fold increases relative to controls. Fatty acid composition was modified under UV-C treatment, including increased oleic acid levels and the detection of docosahexaenoic acid (DHA), supporting potential functional food applications. Biodiesel properties, calculated from fatty acid methyl ester profiles, showed cetane numbers exceeding EN 14,214 minimum requirements, however, the cold-flow properties (CP and CFPP) of both species failed to meet the standard specifications. Overall, UV-C irradiation modulated biomass accumulation and metabolite composition, enhancing lipid productivity and altering fatty acid profiles, although further optimization is required to fully meet biodiesel fuel standards.